I am using the below code , But this one is automatically download the PDF file on my local machine. I don,t want to download this by default. I want to show the pdf file on UI  or . 
response.setHeader("Content-Disposition", "attachment;filename=\"" + reportFileName + ".pdf\"");
            response.setContentType(reportType.getContentType());
        Document document = new Document();
        PdfWriter writer = PdfWriter.getInstance(document, response.getOutputStream());
        LavanteReportFooter event = new LavanteReportFooter();
        writer.setPageEvent(event);         
        document.open();
        PdfPTable table = new PdfPTable(reportColumnHeaders.size());
        table.setWidthPercentage(100); //Width 100%
        table.setSpacingBefore(10f); //Space before table
        table.setSpacingAfter(10f); //Space after table
        Font pdfTitleFont = FontFactory.getFont(FontFactory.HELVETICA);
        pdfTitleFont.setSize(12f);
        pdfTitleFont.setStyle(Font.BOLD);
        Paragraph pdfTitle = new Paragraph(reportFileName, pdfTitleFont);
        pdfTitle.setAlignment(Element.ALIGN_LEFT);
        PdfPCell pdfTitleCell = new PdfPCell(pdfTitle);
        pdfTitleCell.setBackgroundColor(Color.WHITE);
        pdfTitleCell.setHorizontalAlignment(Element.ALIGN_LEFT);
        pdfTitleCell.setColspan(reportColumnHeaders.size());
        pdfTitleCell.setBorder(Rectangle.NO_BORDER);
        table.addCell(pdfTitleCell);
        PdfPCell blankCell = new PdfPCell(new Paragraph(""));
        blankCell.setBackgroundColor(Color.WHITE);
        blankCell.setHorizontalAlignment(Element.ALIGN_LEFT);
        blankCell.setColspan(reportColumnHeaders.size());
        blankCell.setBorder(Rectangle.NO_BORDER);
        table.addCell(blankCell);
        table.addCell(blankCell);
        Font headerFont = FontFactory.getFont(FontFactory.HELVETICA);
        headerFont.setSize(9f);
        for (String reportColumnHeader : reportColumnHeaders) {
            PdfPCell cell = new PdfPCell(new Paragraph(reportColumnHeader, headerFont));
            cell.setPadding(4);
            cell.setHorizontalAlignment(Element.ALIGN_LEFT);
            cell.setVerticalAlignment(Element.ALIGN_MIDDLE);
            cell.setBorderWidth(0.5f);
            cell.setBorderColor(new Color(173, 173, 172));
            cell.setBackgroundColor(new Color(247, 247, 253));
            table.addCell(cell);
        }
        Font dateFont = FontFactory.getFont(FontFactory.HELVETICA);
        dateFont.setSize(8f);
        table.setSplitRows(false);
        table.setComplete(false);
        int rowNum = 1;
        Iterator<List<String>> iterator = dataRows.iterator();
        while (iterator.hasNext()) {
            if(rowNum % 200 == 0){
                document.add(table);
            }
            List<java.lang.String> row = (List<java.lang.String>) iterator.next();
            for (String column : row) {
                PdfPCell cell = new PdfPCell(new Paragraph(column, dateFont));
                if(rowNum % 2 == 0){
                    cell.setBackgroundColor(new Color(247, 247, 253));
                }else{
                    cell.setBackgroundColor(Color.WHITE);
                }
                cell.setPadding(4f);
                cell.setBorderWidth(0.5f);
                cell.setBorderColor(new Color(173, 173, 172));
                cell.setHorizontalAlignment(Element.ALIGN_LEFT);
                cell.setVerticalAlignment(Element.ALIGN_MIDDLE);
                table.addCell(cell);
            }
            row.clear();
            iterator.remove();
            rowNum = rowNum +1;
        }
        table.setComplete(true);
        document.add(table);
        document.close();
        writer.close();
    }